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Host eye after corneal transplantation and suturing of limbal graft

FIGURE 4.11 Transplantation of allogeneic limbal segments to restore corneal epithelium. (A) The limbal tissue and, if necessary, the cornea, were removed from the donor eye. (B) The diseased fibrovascular tissue was removed from the host eye to expose the corneal stroma and a sheet of amniotic membrane was applied as a substrate for re-epithelialization and to reduce inflammation. The limbal graft was then sutured in around the rim of the eye. If the host stroma was diseased, it was removed and the donor corneal button transplanted as well. (C) Results of the operation in a 32 year old woman with Stevens-Johnson syndrome. Top, the opaque ocular surface. Middle, donor limbal tissue (arrow) sutured in place. Bottom, Seventeen months after surgery a large portion of the cornea is clear. Reproduced with permission from Tsubota et al., Treatment of severe ocular-surface disorders with corneal epithelial stem-cell transplantation. New Eng J Med 340:1697-1703. Copyright 1999, Massachusetts Medical Society.

recipient cornea was removed and a donor cornea was allografted in addition to the limbal tissue. A clear cornea was established and vision improved in 35% of the 43 eyes transplanted.

These allogeneic transplants required immunosuppression and the rejection rate was high. Therefore, Nishida et al. (2004) used autologous oral epithelium as a source of epithelial cells for cases of total limbal insufficiency FIGURE 4.12. A small piece of full-thickness oral epithelium was excised and enzymati-cally treated to prepare a single cell suspension. The epithelial cells were cultured on one side of a temperature-sensitive polymer, poly(N-isopropylacrylamide), with mitomycin C-treated NIH 3T3 feeder cells on the other side. The polymer is a thin film at 37°C, but reducing the temperature below 30°C causes the

FIGURE 4.12 Regeneration of the cornea by transplantation of autologous epithelial cell sheets grown from oral mucosal epithelium. (A) Oral epithelial cells were grown on temperature-sensitive poly(N-isopropylacrylamide) film at 37°C. The sheet of cells deadheres from the film when the temperature is reduced to 20°C. The sheet is transplanted without sutures to the cornea after removal of scar tissue. The cultured cell sheet (B) resembles corneal epithelium (D) more closely than oral epithelium (C). (E) Electron micrograph of microvilli that developed on the apical surface of the cultured cells. (F-H) Cultured epithelial cell sheets stained with antibodies to keratin 3 (F), integrin pi (G), and the epithelial cell marker p-63 (H). Scale bars in B, F, G and H = 50 |m; scale bars in C, = 100 |m.

FIGURE 4.12 Regeneration of the cornea by transplantation of autologous epithelial cell sheets grown from oral mucosal epithelium. (A) Oral epithelial cells were grown on temperature-sensitive poly(N-isopropylacrylamide) film at 37°C. The sheet of cells deadheres from the film when the temperature is reduced to 20°C. The sheet is transplanted without sutures to the cornea after removal of scar tissue. The cultured cell sheet (B) resembles corneal epithelium (D) more closely than oral epithelium (C). (E) Electron micrograph of microvilli that developed on the apical surface of the cultured cells. (F-H) Cultured epithelial cell sheets stained with antibodies to keratin 3 (F), integrin pi (G), and the epithelial cell marker p-63 (H). Scale bars in B, F, G and H = 50 |m; scale bars in C, = 100 |m.

film to hydrate rapidly, allowing detachment of the sheets formed by the epithelial cells. The epithelial cell sheets were applied to the corneal surface without sutures after removal of scar tissue. Four patients were autografted in this way, and all had significantly improved vision. The corneas remained clear over 15

months of follow-up. The corneal epithelium is regenerated by stem cells in the mucosal epithelium, the presence of which was demonstrated by colony-forming assays.

There have been numerous attempts to construct bioartificial corneas (Trinkaus-Randall, 2000). Perhaps the most successful have been corneal equivalents constructed from immortalized cell lines derived from each layer of the human cornea (Griffith et al., 1999). These cells were seeded into a collagen-chondroitin sulfate scaffold crosslinked with glutaraldehyde and the construct was cultured for two weeks. The differentiated constructs were transparent and responded to irritation in the same way that natural human and rabbit corneas do. While these bioartificial corneas have not yet been used to replace diseased and injured corneas, they have applications as alternatives to animal models to evaluate chemicals as irritants, and to study wound healing and cell-matrix interactions.

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How To Reduce Acne Scarring

How To Reduce Acne Scarring

Acne is a name that is famous in its own right, but for all of the wrong reasons. Most teenagers know, and dread, the very word, as it so prevalently wrecks havoc on their faces throughout their adolescent years.

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